Layered product for packaging

ABSTRACT

A packaging material being a laminate formed by an outer layer comprising a laminated film which in turn is constituted by a cellophane sheet and easy-to-cut plastic film, and an inner layer comprising hot-melt material coating, wherein said packaging material allows for easy manufacturing control and storage control and offers good cutting properties in all directions when cut while a block of cheese or other food is packaged inside.

TECHNICAL FIELD

The present invention relates to a layered product for packaging which is suitable for contact packaging of food items that are cut into pieces with a knife, such as block-shaped cheese or cakes of sweet bean jelly or rice powder jelly.

The present invention also relates to a layered product for packaging having good cutting property where it can be cut into pieces with a knife in any direction.

To be more specific, the present invention relates to a layered product for packaging characterized in that it is formed by an outer layer comprising a laminated film which in turn is constituted by a cellophane sheet and easy-to-cut plastic film, and an inner layer comprising hot-melt material.

It should be noted that, in this context of the present invention, the “inner layer” refers to the layer on the side that comes in contact with food, while the “outer layer” refers to the layer on the side which is exposed to the exterior.

PRIOR ART

Conventionally, a closely-attached packaging method for preventing the surface of food from being exposed to air is known, in which as packaging materials for block-shaped cheese and other foods, cellophane or plastic films coated with a closely-attachable thermoplastic resin are used on the surface contacting with food, and these packaging materials are used commonly as essential methods for preventing food from degrading or growing mould and thereby losing its freshness during distribution for sale.

Further, materials used for directly packaging food include a moisture-proof cellophane sheet (cellophane sheet coated with vinylidene chloride resin) or plastic film that has been laminated with an aluminum foil and coated with resin and wax in order to add water-proofing properties, moisture-proofing properties, gas barrier properties and heat sealing properties (Patent Literature 1) and a laminated film comprising an outer layer which is constituted by a plastic film, metal foil or other gas barrier material having fine holes in it, and an inner layer comprising wax (Patent Literature 2).

In general, food packaged in any of these packaging materials is rarely eaten at once in its entirety, but instead it is normally cut into blocks of desired sizes or shapes for eating and saved in such blocks, and therefore packaging materials used for packaging this type of food must have not only excellent preservation properties but also excellent cutting property that allows it to be cut with a knife.

-   Patent Literature 1: Japanese Patent Laid-open No. Hei 06-040485 -   Patent Literature 2: Japanese Patent Laid-open No. Hei 11-292184

SUMMARY OF THE INVENTION Problems to Be Solved by the Invention

Currently, materials for packaging block-shaped cheese and other similar types of food commercially available on the market are mostly constituted by a single cellophane layer. These packaging materials constituted by a single wax-coated cellophane layer offer good contact property with food, but they are likely to develop pinholes if a severe impact is applied to them during transportation. Aluminum foil laminated plastics also have other problems, such as metal detectors not functioning favorably in the manufacturing process. On the other hand, use of a plastic film partially or entirely over these packaging materials to prevent the aforementioned problems causes a new set of problems that include loss of cutting property when cut with a knife and consequent loss of product value.

In addition, these packaging materials have 70 to 130 g/m² of hot-mail material coated on the inner surface that comes in contact with food in order to accomplish sealing under pressure at normal temperature. As a result, the viscosity on the coated side becomes higher than necessary and if these packaging materials are stored in rolls at normal temperature the film itself tends to undergo blocking before use, and therefore there is a problem in handling these packaging materials prior to their use.

Considering the above, these packaging materials must be coated with cornstarch during the manufacturing process of film and also refrigerated for storage, in order to prevent the film from sticking to itself while the materials are in storage before use. However, the use of cornstarch on the surface of packaging material causes a problem of powder scattering while manufacturing, making process control difficult.

On the other hand, an attempt to apply a thin coat of thermal melting wax to prevent film blocking causes the packaging material to shrink due to the heat in the wax application process.

Patent Literatures 1 and 2 report inventions relating to packaging materials for blocks of cheese, but the invention described in Patent Literature 1 provides good tearing property only in one direction and thus cannot be used by dicing it, etc. Furthermore, the need to apply at least 40 g/m² of hot-melt material on the surface of this packaging material makes it difficult to implement manufacturing control and storage control. On the other hand, the invention described in Patent Literature 2 offers good cutting property in all directions. However, its physical strength may drop depending on the size of fine holes provided in the film to add easy cutting property to the film, which can then make it difficult to implement lamination, wax coating and other secondary processing.

Accordingly, packaging materials are desired which solve these problems by offering a desired physical property, or specifically good cutting property in all directions, while also making it easy to implement production control and storage control.

Means for Solving the Problems

The present invention was developed following the achievement of a layered product for packaging comprising an outer layer which in turn is constituted by a laminated film made up of easy-to-cut plastic film and cellophane sheet, wherein said packaging material offers good cutting property in all directions when cut with a knife; undergoes little thermal shrinkage or breaks of packaging materials during manufacturing; and offers a good anti-pinhole property.

In addition, the layered product for packaging proposed by the present invention keeps to only approx. 10 to 40 g/m² the coating amount of hot-melt material to be coated as a inner layer that comes in contact with food, and also makes it no longer necessary to use cornstarch to prevent the packaging material from sticking to itself, thereby making it possible to ease production control and storage during the manufacturing of packaging material.

Effects of the Invention

The layered product for packaging proposed by the present invention maintains good cutting property in all directions when cut with a knife, while undergoing little thermal shrinkage or breaking during the manufacture of packaging material and also offers a good anti-pinhole property, because said packaging material is made by using a cellophane sheet as the base material and laminating this base material with an easy-to-cut plastic film.

In addition, the present invention does not require use of cornstarch, which in turn makes it easy to implement quality control of the packaging material, eliminates the need for refrigeration during storage, and consequently improves the efficiency of production.

In view of the improved physical properties mentioned above, the packaging material proposed by the present invention is the most suitable for block-shaped cheese and other similar food items because it can reduce the probability of development of pinholes while offering good cutting property in all directions when cut with a kitchen knife or a pocketknife.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Enlarged sectional view showing the constitution of a conventional packaging material

FIG. 2 Enlarged sectional view showing the constitution of the packaging material given in Example 1 that conforms to the present invention

FIG. 3 Enlarged sectional view showing the constitution of the packaging material given in Example 2 that conforms to the present invention

FIG. 4 Oblique view explaining a cutting property test, using a knife, of a packaging product given in an example of the present invention, where said product is used for packaging cheese

DESCRIPTION OF THE SYMBOLS

-   1 Cellophane sheet -   2 Hot-melt material -   3 Cornstarch -   4 Easy-to-cut plastic film -   5 Cutting line in TD direction -   6 Cutting line in MD direction

EXAMPLES

The following explains the details of the present invention based on drawings that illustrate examples.

FIG. 1 is an enlarged sectional view showing the constitution of a conventional packaging material, while FIGS. 2 and 3 are enlarged views showing the constitutions of packaging materials given in examples that conform to the present invention, while FIG. 4 is an oblique view explaining a cutting property test, using a knife, of a packaging product given in an example of the present invention.

As shown in FIG. 1, the conventional packaging material is constituted by a cellophane sheet 1 being the base material, with a hot-melt material 2 having adhesive properties coated on the surface of the side that comes in contact with food such as a block of cheese, after which cornstarch 3 is applied on top as a blocking prevention material to prevent blocking.

Further, as shown in FIG. 2 the packaging material given in this example that conforms to the present invention is constituted by a cellophane sheet 1 being the base material, with easy-to-cut plastic film 4 laminated on the side that comes in contact with food such as a block of cheese, after which hot-melt material 2 having adhesive properties is coated on top, constituting a layered product.

The easy-to-cut plastic film 4 used in the present invention may have a single-layer structure or multi-layer structure, but it is particularly desirable to use a laminate having a three-layer structure, preferably with the quality of the middle layer improved by adding brittleness to it. Among appropriate easy-to-cut plastic films having such property are drawn polyester films.

In addition, ethylene vinyl alcohol, paraffin wax and microcrystalline wax are among materials that are suitable as the thermoplastic resin to constitute the hot-melt material 2 used in the packaging material proposed by the present invention,

In Example 1, a laminated film comprising a (A) polyester film having a multi-layer structure with a physically brittle layer used as the middle layer, and a (B) moisture-proof cellophane sheet laminated with the foregoing, was created, with 10 to 40 g/m² of hot-melt material coated on the aforementioned polyester film (A) side using a roll coater, and this laminated film was used to conduct a physical property evaluation and cutting property test using a knife.

In Example 2, a laminated film comprising a (A) polyester film physically embrittled by mechanically scratching the film surface, and a (B) moisture-proof cellophane sheet laminated with the foregoing, was created, with 10 to 40 g/m² of hot-melt material coated on the aforementioned polyester film (A) side using a roll coater, and this laminated film was used to conduct a physical property evaluation and cutting property test using a knife.

As a comparative example, 100 g/m² of the aforementioned thermal melting wax was coated on one side of a cellophane sheet coated with a vinylidene chloride resin, which is traditionally known as a packaging material offering good cutting property when cut with a knife, and the resulting product was used to conduct a physical property evaluation and cutting property test using a knife.

Each packaging material was used to package 225 g of block-shaped processed cheese. Sensory evaluations were conducted by ten males and females in their 20s to 50s, evaluating each cheese samples for the cutting property using a knife.

The results are shown in Table 1.

TABLE 1 Exam- Exam- Comparative ple 1 ple 2 example Thickness (μm) 92 to 96 92 to 96 115 to 125 Tearing strength (mN) TD 228 208 188 MD 166 161 160 Piercing strength (N) 7.2 7.1 7.9 Oxygen permeation degree 1.6 1.8 4.0 (cc/m² · day/atm) Steam permeation degree 4.8 5.0 10.0 (g/m²/24 hrs) Cutting property when cut with a TD Good Good Good knife while food is inside MD Good Good Good

In the sensory evaluation involving ten males and females in their 20s to 50s, the packaging materials in both Examples 1 and 2 were evaluated as having good cutting property in both the TD direction and the MD direction, just like the packaging material in the comparative example.

In addition, the packaging materials in both Examples 1 and 2 are deemed to offer greater preservability than the packaging material in the comparative example, in light of their oxygen permeation degree and steam permeation degree. 

1. A layered product for packaging characterized in that an outer layer is formed of a laminate film of a cellophane sheet and easy-to-cut plastic film, and an inner layer is formed of a hot-melt material.
 2. The layered product for packaging according to claim 1, characterized in that the easy-to-cut plastic film that forms the outer layer is constituted by polyester.
 3. The layered product for packaging according to claim 1, characterized in that the easy-to-cut plastic film that forms the outer layer is constituted by a three-layer structure which is formed of polyester comprising a physically brittle layer as a middle layer, and/or which is formed of polyester having a film surface physically embrittled by mechanically scratching the film surface.
 4. The layered product for packaging according to claim 1, characterized in that the hot-melt material that forms the inner layer is coated with 10 to 40 g/m².
 5. The layered product for packaging according to claim 2, characterized in that the hot-melt material that forms the inner layer is coated with 10 to 40 g/m².
 6. The layered product for packaging according to claim 3, characterized in that the hot-melt material that forms the inner layer is coated with 10 to 40 g/m².
 7. A knife-cuttable layered product for food packaging, comprising: a laminate consisting of a cellophane sheet and an easy-to-cut polyester film, said easy-to-cut polyester film comprising a physically embrittled polyester layer; and a hot-melt coating coated on a surface of the easy-to-cut polyester film in an amount of 10 to 40 g/m², said hot-melt coating being adapted to be in immediate contact with food packaged by the layered product.
 8. The layered product for food packaging according to claim 7, wherein the easy-to-cut polyester film comprises other polyester layers, and the physically embrittled polyester layer which is more brittle than the other polyester layers is a middle layer sandwiched between the other polyester layers.
 9. The layered product for food packaging according to claim 7, wherein the easy-to-cut polyester film is a polyester film having a surface mechanically scratched without penetrating through the polyester film, so as to embrittle the polyester film.
 10. The layered product for food packaging according to claim 7, which consists of the laminate and the hot-melt coating.
 11. A packaged food, comprising: the knife-cuttable layered product according to claim 7; and a food packaged by the layered product wherein the food is in immediate contact with the hot-melt coating, wherein the layered product is cuttable in multiple directions for each serving with the food packaged inside, using a kitchen knife or pocketknife.
 12. The packaged food according to claim 11, wherein the food is selected from the groups consisting of cheese, sweet bean jelly, and rice powder jelly.
 13. The packaged food according to claim 11, wherein the easy-to-cut polyester film comprises other polyester layers, and the physically embrittled polyester layer which is more brittle than the other polyester layers is a middle layer sandwiched between the other polyester layers.
 14. The packaged food according to claim 11, wherein the easy-to-cut polyester film is a polyester film having a surface mechanically scratched without penetrating through the polyester film, so as to embrittle the polyester film.
 15. The packaged food according to claim 11, wherein the layered product consists of the laminate and the hot-melt coating. 